1. Field of the Invention
The present invention relates to a liquid crystal display and, particularly, to a configuration of lead portions provided in a peripheral portion of a display panel of the liquid crystal display.
2. Description of the Prior Art
The liquid crystal display is used popularly as a flat panel display, which is thin, lightweight and low power consumption. A conventional liquid crystal display is constructed with a liquid crystal display panel having a display pixel portion for displaying a desired image on the basis of scan signals and data signals inputted to scan lines and signal lines thereof and a peripheral portion arranged in a peripheral portion of the display pixel portion as a frame. In the peripheral portion, connecting terminals are arranged so that terminals of a TCP (Tape Carrier Package) with a drive IC for supplying the scan signals and the data signals are connected thereto. And lead wires are arranged for connecting the connecting terminals to the scan lines and the signal lines for a display area.
A liquid crystal of the liquid crystal display is sealed in between opposing substrates of the liquid crystal display panel by a liquid crystal sealing member. The liquid crystal sealing member is also positioned in the peripheral portion of the liquid crystal display and crosses the lead portions in an overlapping relation.
FIG. 1 is a partially enlarged plan view of the peripheral portion of the conventional liquid crystal display, showing a portion thereof to which one TCP is connected. In FIG. 1, scan lines and data lines derived from a display pixel portion 101 are connected to a plurality of connecting terminals 104 orderly arranged in the peripheral portion through lead wires 103, respectively.
As shown in FIG. 1, one of the lead wires, which is connected to a center one of the connecting terminals 104, is shortest and the length of connecting wire is increased with increase of distance of a corresponding connecting terminal from the center connecting terminal. With such difference in length between the lead wires, resistance values of the lead wires become different. Therefore, degree of deformation of scan signal waveform and the data signal waveform supplied through the lead wires to the display pixel portion becomes different correspondingly to the difference in length between the lead wires even when identical scan signals and data signals are supplied from the connecting terminals to the display pixel portion. Consequently, voltages to be written in respective pixels become uneven, causing luminance of the liquid crystal display panel to be reduced or increased. Unevenness of resistance value of the lead wires connected to the scan lines appears on the panel as horizontal line variation of luminance in a vertical direction and unevenness of resistance value of the lead wires connected to the signal lines appears on the panel as vertical variation of luminance in a horizontal direction.
In order to solve the above problem, it is usual in the conventional liquid crystal display to average resistance values of the lead wires connected to one TCP. For example, width of the lead wire connected to the connecting terminal arranged remote from the center connecting terminal is made large compared with that of the lead wire connected to the center connecting terminal.
JP 2000-56724 A discloses a technique for averaging length of lead wires by forming only one bent portion in each of the lead wires.
There is a recent request of enlargement of an area of a display pixel portion of a liquid crystal display panel and reduction of an area of a peripheral portion, that is, a frame portion, of a liquid crystal display. When, in order to satisfy the request of reduction of the frame area, width of the peripheral portion is reduced, a space for arranging the lead wires is reduced necessarily. Therefore, the prior proposal of width increase of the lead wire or formation of the bent portion becomes impossible in view of possible short-circuit between adjacent lead wires. Consequently, it is necessary to provide other means for equalizing the resistance values of the lead wires.